diff --git a/README.md b/README.md
index 409c80e..12fe1b8 100644
--- a/README.md
+++ b/README.md
@@ -13,7 +13,7 @@ _Vows_ is an experiment in making this possible, while adding a minimum of overh
 
 synopsis
 --------
-    
+
     var vows = require('vows'),
         assert = require('assert');
 
@@ -25,7 +25,7 @@ synopsis
 
 In the example above, `question()` would be a function which returns an `EventEmitter`.
 When the `"success"` event is emitted, the function passed to `addVow` is run,
-and the results output to the console. 
+and the results output to the console.
 
 Vows are run as soon as the promise completes, so the order in which they are run is undefined.
 
@@ -38,33 +38,35 @@ writing specs
 -------------
 
     vows.describe('A Database library').addVows({
-        // run this once, and execute the following tests when it completes
-        topic: function () { return new(DB) },
-
-        'set() should store a k/v pair': {
-            // the inner context gets the return values of the outer contexts
-            // passed as arguments. Here, `db` is new(DB).
-            topic: function (db) { return db.set('pulp', 'orange') },
-            
-            // `res` is the value emitted by the above `db.set`
-            'and return OK': function (res) {
-                assert.equal(res, "OK");  
+        'A DB object': {
+            // run this once, and execute the following tests when it completes
+            topic: function () { return new(DB) },
+
+            'set() should store a k/v pair': {
+                // the inner context gets the return values of the outer contexts
+                // passed as arguments. Here, `db` is new(DB).
+                topic: function (db) { return db.set('pulp', 'orange') },
+
+                // `res` is the value emitted by the above `db.set`
+                'and return OK': function (res) {
+                    assert.equal(res, "OK");
+                },
+                'and when checked for existence': {
+                    // here, we need to access `db`, from the parent context.
+                    // It's passed as the 2nd argument to `topic`, we discard the first,
+                    // which would have been the above `res`.
+                    topic: function (_, db) { return db.exists('pulp') },
+
+                    'return true': function (re) {
+                        assert.equal(re, true);
+                    }
+                }
             },
-            'and when checked for existence': {
-                // here, we need to access `db`, from the parent context.
-                // It's passed as the 2nd argument to `topic`, we discard the first,
-                // which would have been the above `res`.
-                topic: function (_, db) { return db.exists('pulp') },
-
-                'return true': function (re) {
-                    assert.equal(re, true); 
+            'get()': {
+                topic: function (db) { return db.get('dream') },
+                'should return the stored value': function (res) {
+                    assert.equal(res, 'catcher');
                 }
             }
-        },
-        'get()': {
-            topic: function (db) { return db.get('dream') },
-            'should return the stored value': function (res) {
-                assert.equal(res, 'catcher'); 
-            }
         }
     });
diff --git a/lib/vows.js b/lib/vows.js
index 784192c..c0b1856 100644
--- a/lib/vows.js
+++ b/lib/vows.js
@@ -210,6 +210,9 @@ function addVows(tests) {
     vows.promises.push(promise);
 
     if (typeof(tests) === 'object') {
+        if ('topic' in tests) {
+            throw new(Error)("Missing top-level context.");
+        }
         // Count the number of vows/promises expected to fire,
         // so we know when the tests are over.
         // We match the keys against `matcher`, to decide